BAK knockdown delays bleaching and alleviates oxidative DNA damage in a reef-building coral

Climate change is rapidly pushing coral reefs towards extinction. Efforts to restore and protect these ecosystems using resilient corals are increasing, but our understanding of cellular mechanisms of thermal resilience and trade-offs remains limited. Here, we demonstrate downregulation of pa-BAK slows bleaching and stabilizes the symbiosis during acute heat stress in Pocillopora acuta . Counterintuitively, oxidative DNA damage – a hallmark of the thermal stress response in corals – was prevented in corals with such “forced” symbiosis stability, possibly through alterations in mitochondrial ROS release. Using expression data of genes representing various stress-response pathways, we propose a model that coral heat stress response is mediated via the AMPK/Foxo3/Nrf2 signaling network. Developing our understanding of heat-stress defense mechanisms promoting stability in the coral-algal symbiosis is fundamental for effective modern coral reef restoration practices based on improving system resilience.